The object of the invention is, more specifically, the preparation step which consists, after slaughtering and evisceration, in pulling off or loosening off the two layers of fat lining the inner faces of the hog's sides, these layers of fat being normally known as "belly strips".
One known process for loosening and pulling off such belly strips consists, according to French Patent 2 597 721 (86-06360), in suspending the eviscerated hog carcass by its hind legs, introducing into the hog's open rib cage, a clamp equipped with outwardly-facing active jaws, placing said active jaws substantially inside the plane of the lower ends of the belly strips lining the inner faces of the hog's sides, opening the clamp in order to apply the active jaws against the lower ends of the strips, pressing against the external faces of the hog's sides passive counter-jaws situated in facing relationship to the active jaws, bringing out said active jaws means for gripping the belly strips simultaneously, opening the passive counter-jaws, closing the clamp so as to bring the active jaws close together and pulling off the lower ends of the belly strips gripped by the gripping means, and finally raising up the clamp in order to detach the belly strips from the inner faces of the hog's sides and bringing said clamp out.
Said patent further relates to a machine for carrying out the aforesaid process, which machine comprises a supporting structure movable vertically by means of a motor, over supporting and guiding rails mounted on a frame, a chassis carried by said structure and which is horizontally movable by means of a motor and forms a vertical pivot, and a two-branched clamp mounted on the pivot.
The process and machine according to said patent have been found satisfactory for gripping, pulling and loosening off the belly strips.
Practical use, however, has revealed that control of the machine in automatic working of the process did raise a problem, heretofore unsolved, resulting from the succession, in an automatic slaughtering line, of hogs of different morphology and sizes, and also suspended at different heights.
To perform a completely automatic process, it is important for the belly strips to be gripped in the vicinity of their lower part. Yet, the fact that these lower parts are situated in the horizontal plane, makes way for considerable variations linked to the morphology and size of the hogs.
In a mass-slaughtering line, differences in sizes of suspended hogs of between 1,500 mm and 2,200 mm may be found.
Such differences make it difficult to define a gripping and stripping plane common to all the hogs moving in the line, and as a result, the operation of the machine and implementation of the process described in the aforesaid French patent are often found to vary in efficiency.